Advanced Feedback Control of AC Plasmas

Many plasma physics experiments not only further the understanding of the behavior of plasmas but also pursue nuclear fusion as a safe, clean, and reliable energy source. A common problem for these experiments is a lack of effective feedback control on microsecond timescales. Plasmas can deviate from their nominal parameters on such timescales and faster corrections help ensure the plasma stays within a desired parameter space. An emerging solution is utilizing the highly parallel nature of graphics processing unit (GPU) architecture to simultaneously process all relevant data and compute the appropriate feedback signals in microseconds. In Phase I, a new, high-speed digitization and feedback control system will be built, and feedback algorithms developed to simultaneously analyze nine signals and control six separate banks of alternating current (AC) power supplies for a plasma physics experiment. The project goal is to control the imposed voltages and magnetic fluxes within 5% in amplitude and 0.5 microseconds in time. The limits of the technology will be tested as the AC frequency is increased toward 100 kHz. In Phase II and beyond, many more signals will be added to fully utilize the unique capabilities of GPU architecture. Fast equilibrium fitting will also be integrated yielding a whole-device feedback control system with lower latency than similar, central processing unit (CPU)-based systems. The technology will be marketed to public and private, domestic and international, plasma physics experiments as well as any application with many signals and microsecond-scale control needs.